Tele phone



(No Model.)

E. T. GREENFIBLD.

TELEPHONE.

No. 252,294.V

.Patented Jan. 10,1882.

122 venor 9mm/dac ,UNITED *STATES PATENT OFFICE.

i DWIN' rennnNmELD, or BROOKLYN, NY., AssiGNORioF ONE-HALF To THE HOLMES BURGLAR ALARM TELEGRAPH GOMBANY, E New YoRK.

tlafLEPHome.`

SPECIFICATION `forming part of Letters Patent No. 252,294, dated January 10, 1882.

Application tiled ltzlarch-Ez, 1880.

.To all whom it may concern:

Be it known that I, EDWIN T.GREENFIELD, of the-city of Brooklyn, in the State of New York, have invented a new and useful Improvev ment in Telephones, of which the following is a specification;

The present invention relates, primarily, to v the instrument lby means of which atelephonic message is rendered audible at the receiving ro end otthe line; and the object is to provide a` simple and efficient apparatus with `which a` single listener, placed at a centralstation, can keep watch over a large number of'lines con; necting with such station; andthe invention I5 consists, -in a general way, incombining in a single receiving-instrument two or more magnets, electromagnets, orother equivalent devices, according to the number of the lines to be watched and operated.` t 2o The invention is fully illustrated in theaccompanyin g drawings, in which `Figure l is an,

elevation of an instrument adapted for connection `with eight telephonicr'ines, there being four magnets or magnetic bars andtwo helices on each magnet or bar. Fig.`2 is alongitudinal central section ofthe same, audFig. 3 is an end view of the instrument with the earpiece and-diaphragm removed;

Prior to the present invention twomethods 3o had been adopted at the central telephone-station for effecting communication between the various persons whose linesconverge to such By the one method any patron ofthe station. system desirous of being put into communica- 35. tion with any other person is requiredto give a signalfby a bell, or drop, or otherwise, at the central station, whereuponthe attendant connects a telephone to the line of the person signalin g, and through such instrument aseertains with whom he desires communication. Thereupon the second personlis rung up,7 and the proper connection between the two being ef-` l t'ected, the instrument is free for a similar use between other customers; but thetime neces-l sarily consumed in making inquiries and obtaining responses and establishing the desired connections renders it impossible for one attendant to serve more than a very limited number of customers, and in a large office great (No modek) confusion necessarily prevails, and mistakes 5o Aare liable to occur. Moreover, the apparatus requirediu such system, involving,- as it does, extra batteries, resistances, and. other appli.A ances, isnecessarily complicated, expensive, Ianqlliableto derangements. Y

The secondmethod heretofore practiced con` sstsin'l the use ot' a special'signalwire,7 as

itgis called, with which the instrument of each of the customers in tlie system is connected, and wliielifin turn is connected'with receiv- 6o ing and transmitting instrnmentsat the central'station, such instruments being constantly in the hands ofa listener. 4Aside from the extra costof this signalwirmits useis open to `tlieserious objection that'it' there happens a 65 batteny-crossofi' such wire` at any pointa cerl Ltain number ofthe customers,,accordingto the localityvof. the disturbance, willbe en t ott' from `communicationvwith the central. station, and

*the coils equaling in numberthe lines which are to be operated. l, 8 Arepresents the diaphragm; B B, the different magnets g, C C and C C', the coils; and D D, the line-wires, which Ipass through the binding-screws EE, and Dl D ground-wires passing through the binding-screws E E'. 9o

The various line-wires pass lthrough some form of switch-board (not shown in the drawings) before reaching the binding-screws of the reeeiver. When the instrument and conducto'rs are properly -arranged for action-a simple 95 vocal call sent over any one of the lines will be rendered audible to the listeneron77 through the common diaphragm A, whereupon it' is only necessary for the attend ant at the swi tch-board,

receiving his instructions from the listener-on, to connect the lines of the two customers between whom the desired communications are to take place, the wires of such customers being of course disconnected for the time being from the listening-instrument. The eXtreme simplicity of this mechanism compares most favorably with a system which employs callbells or drops with the complicated concomitants of batteries, resistances, Ste.

If at any time any one of the line-wires or conductors becomes crossed with any other Wire, whether it be another wire in the same system or not, the fact is instantly revealed to the listener at the central station; and in order to ascertain which particular line is in trouble it is only necessary for the switchman to disconnect the several lines one by one from the listening-instrument. The moment he disconnects the line which iscrnssed the vlistener becomes aware of the fat-t vby the cessation ofthe sounds which previously hail apprised him of the iactofthe existenceofthedifiiculty. Under this system the disturbance caused by a cross is limited to the particular line wherethe cross occurs, and 'this fact, coupled with the prompt ascertainine'n't ofthe existence and of the location ofthe dicnlty, is manifestly a great advantage as compared with the operation of a system in which a cross disturbs all the customers w'ho connect with the same signal-Wire, and` in which, when a cross occurs, there may be required aprolonged search to locate it. Moreover,`if a break occurs in any one of' the lines connected with this compound receivinginstrument', it cuts ott' from the central station only theone customer who is served. by such line, while in the case of the system using a signal-wire a break in such wire is liable to cut ott" themajority of the customers.

In order to seeurecompactness of construction, two or more helices may be arranged on each of the magnets used, as clearly shown-in Fig. 2, these several coils 'being respectively connected with the separate line-Wires.

The several magnets maybe connected together by means of an ir'on yoke orbridge-piece,

' Gr. The use of such bridge-piece serves to strengthen the action of the magnets on the diaphragm', and also distributes the electric imipulse communicated to anyone of them equally on all sides ofthe axial line otl theinstrument, and thus secures greater uniformity of action upon the diaphragm than would otherwise result. It', however, no bridge-piece or yoke G be used, (and its use is not regarded as indispensable,) the magnets will be entirely independent of each other.

Instead of using a separate binding-screw for each ot' the groundwires,it is plain that these several wires maybe twisted together and passed through a single bindingscrew, and thence to the earth.

It is also plain that the principle involved in thisinvention would be, applicable to the use in the receiver of other devices than magnets or electro-magnets connected with the linewires for giving vibratiorto the common plate, or other instrumentality whereby sonorous-vibration is communicated to the air, or the sound-waves passed along the wires to the receiver are ampliiied.

The instrument above described, ywhile intended primarily as a receiving-instrument, may also be used as a multiple transmitter, being capable o f transmitting simultaneously as many messages as there are separate line-wires or conductors;-.but l'or this purpose it ispreferredl to use a battery-current in connection with induction-coils, as set forth in a separateapplication therefor tiled by me conteinporaneously herewith. l What is claimed as new is l1. A telephone provided with two or more magnets or equivalent devices, arranged to connect with two or more independent linewires, substantially as described.

2. The combination, in a telephone, of two or more independent helices, arranged upon the same magnet or bar and connecting with separate line-wires, substantially as and for the purpose set forth. c

3. The combination of two ormore independent line-wires with one receiving-telephone, for

the purposes set forth. 4

4. rPhe combination ot'two or more telephonie conductors with one telephone by means of a plurality of magnets or equivalent devices,

l substantially as described;

5. The combination of two or more magnets or equivalent devices, arranged in a single telephone, and provided with independent helices connecting with separate line-wires, and a yoke connecting the poles ofthe magnets, substantially as described.

6.. The combination, in a telephone, of two or more independent helices connecting with IOC .IOS

independent line-wires, substantiallyas and for thepnrposes set forth.

. EDWIN T. GREENFIELD.

Witnesses: n

BENJ. A. SMITH, SAML. A. DUNCAN. 

